Preparation of Mo6+, Gd3+-doped TiO2 nanotube arrays and study of their organization and photocatalytic properties

Titanium dioxide nanotube arrays doped with Mo 6 + , Gd 3 + , and Mo 6 + - Gd 3 + were prepared by anodic oxidation combined with a two-step electrochemical method. The crystalline structure, surface morphology, light absorption properties, and crystalline transformation process were characterized using XRD, SEM, UV–Vis, DSC, and FT-IR. The results show that Mo 6 + and Gd 3 + single doping of TiO 2 can promote the transformation of amorphous TiO 2 to anatase and inhibit the transformation of anatase phase to rutile, but Mo 6 + – Gd 3 + co-doping promotes both phase transformations, and the anatase compositions of the TiO 2 heat-treated at 450 ∘ C were all over 91%; The tube diameters of TiO 2 nanotubes were all around 60–70 nm; the Mo 6 + - and Gd 3 + -doped TiO 2 light absorption peaks were all significantly red-shifted, with the most obvious change in the Mo 6 + – Gd 3 + co-doping, where the forbidden bandwidth was reduced to 3.01 eV; The degradation rate of pure TiO 2 photocatalytic degradation of methylene blue for 8 h was only 41.9%, while the degradation rate of Mo 6 + – Gd 3 + co-doped TiO 2 was as high as 91.51%; Mo 6 + , Gd 3 + , single doping and co-doping could increase the amount of •OH, •OOH adsorbed on the surface of TiO 2 , which led to the improvement of catalytic performance.